This invention relates to an improvement in a seed drill of the type disclosed in my U.S. Pat. No. 3,177,830, which was issued on Apr. 13, 1965. A modification of this type of seed drill was disclosed in my U.S. Pat. No. 3,319,590, issued May 16, 1967. The disclosures of these two prior patents are hereby incorporated within this disclosure by reference.
The seed drills disclosed in my referenced U.S. Patents are designed for deep furrow seeding of crops. Seed is planted at the bottom of a furrow having packed sloped sides. This is accomplished by placing the seeds into soil behind a narrow shovel overlapped closely by single or paired press wheels. Each pair of press wheels is mounted alongside the path of a shovel to pack the sloping sides of a deep furrow and assure accurate control of both planting depth of the seeds and soil coverage over the seeds.
When such seed drills are used, the weight of the mobile frame, the negative draft created by the shape of the shovel and interposed compression spring forces cooperatively maintain the shovel at a subsoil elevation to place seeds in moist soil at the bottom of the subsequently-packed furrow sides. The shovels are each fixed at the lower end of a rigid seed boot, which is in turn fixed to the rear end of elongated drag bar assemblies. The drag bar assemblies are transversely pivoted at their forward ends and can be raised or lowered through a spring biased mechanical connection between the mobile frame and the individual drag bar assemblies. While the drag bar assemblies are normally biased downwardly through an interposed compression spring, the elongated moment arm between the forward pivot connections and the rearward shovel minimizes upward movement of the shovel due to soil obstructions. Upward movement is also virtually prevented by the substantial compressive forces needed to assure proper engagement of moist soil by the individual shovels. While my patents mention that the shovels can move upwardly to clear rocks and field obstructions, these statements have been proven overly optimistic in actual practice.
To avoid destruction of shovels and/or supporting seed tubes when engaging an obstruction such as a rock, it has been common to connect the upper end of the seed tube to the rear end of the individual drag bar assemblies through a frictional pivot connection, and to fix them to one another by means of a shear pin that will break before serious damage occurs to the shovel or seed tube. Similar damage to the adjacent press wheels is not a significant problem, since their rolling engagement with the soil permits the press wheels to roll over engaged obstructions.
Since seed drills are commonly used to simultaneously seed parallel rows across a wide field swath by operation of multiple units, the operator of a tractor pulling such drills cannot be always aware of the breakage of individual shear pins. When this occurs, the loosely depending seed boot and shovel will continue to be dragged between the press wheels, but will not effectively place seed as required for planting purposes. This results in skipped areas along intended seed rows and can affect planting efficiency and resulting crop production levels. Furthermore, the breakage of a shear pin, when detected, requires that the entire drill be stopped, the broken pin segments be removed, the seed drill and shovel be manually repositioned, and that a new shear pin be reinstalled between the seed tube and drag bar assembly. This is not only time consuming and difficult under field conditions, but requires the operator to have tools and repair parts always available in order to minimize down time during critical seeding periods.
The present invention arose as part of an effort to improve the efficiency of such seeding operations. It provides an automatic trip mechanism that replaces the shear pin connections and permits the shovel to clear field obstructions by momentarily pivoting rearwardly and then automatically returning to its normal planting position. The entire operation occurs without human intervention during normal forward travel of the drill. It requires no down time or manual repair to the equipment. Further development has refined the mechanism to incorporate adjustment features that permit the user to adapt the drill components to individual field conditions and planting requirements. The otherwise rigid connection that has been used to mount such furrow openers in the past can now mimic the flexible soil engaging operations of a spring tooth shovel, which constantly vibrates back and forth to match soil conditions and facilitate opening of the required furrow. This is particularly advantageous when utilizing this type of drill in minimum or no-till yield operations, where greater soil compactness and soil variations are encountered, as well as varying draft loads due to field trash conditions posed by earlier crop residues.
The automatic trip mechanism utilizes an elongated leaf spring of a type very readily available in automotive and related fields. It can be readily mounted to existing drills or incorporated within the structure of new drills as they are designed and manufactured.